The article explains it plainly: they weren't getting the message to business people that Gmail on Google Apps isn't scanned despite free Gmail being, so they stopped scanning Gmail altogether.
[0] http://www.thecrimson.com/article/2016/3/23/alumni-lawsuit-a...
Note that this is not what the article says. It says that they stopped scanning Gmail for ads, but does not say they stopped scanning email for non-ad purposes.
I can't find a citation, but I'm fairly confident that that's never been the case. Ad targeting from emails has always been siloed to within gmail. To quote the post:
>Consumer Gmail content will not be used or scanned for any ads personalization after this change.
That's pretty unequivocal.